Hydraulic actuators

ABSTRACT

The invention provides a hydraulic motor and actuating means therefor comprising means defining a first space capable of containing pressurised gas, means defining a second space capable of containing hydraulic liquid, wall means sealingly separating said first and second spaces, said wall means being constructed and arranged to permit changes in the volume of said first space, means for introducing pressurised hydraulic liquid in said second space so as to reduce the volume of said first space compressing the gas, said second space being connected to the hydraulic motor and valve means for controlling communication between said second space and the hydraulic motor.

United States Patent [111 3,861,144

Woods Jan. 21, 1975 I HYDRAULIC ACTUATORS [75] Inventor: Norman Harry woods, Primary ExaminerEdgar W. Geoghegan Bournemouth England Attorney, Agent, or FirmWatson, Cole, Grindle &

Watson [73] Assignee: Normar Engineering Company Limited, Bournemouth, England 22 Filed: Aug. 14, 1973 [57] ABSTRACT [21] APPL 388 123 The invention provides a hydraulic motor and actuat ing means therefor comprising means defining a first space capable of containing pressurised gas, means do- [52] U.S. Cl 60/386, 60/402, 60/413 fining a second pace capable of containing hydraulic v [51] Int. Cl. ..F15b 1/02 liquid, wall means sealingly separating said first and 1 Fleld 0f Search-m- 14 second spaces, said wall means being constructed and 0/ 0 405 arranged to permit changes in the volume of said first space, means for introducing pressurised hydraulic liql References Cited uid in said second space so as to reduce the volume of UNITED STATES PATENTS said first space compressing the gas, said second space 2,628,476 2 1953 Grier 60/413 x being conneted the hydraulic motor and 2,802,452 8/1957 means for controlling communication between said 2,886,947 5/1959 Jenny 60/402 Second P nd the hydraulic mOtOI.

FOREIGN PATENTS OR APPLICATIONS 12 Claims, 1 Drawing Figure 630,399 11/1961 Canada 60/402 1 HYDRAULIC ACTUATORS BACKGROUND OF THE INVENTION This invention relates to an apparatus for actuating a hydraulic motor, and more particularly is concerned with an apparatus for actuating a hydraulic motor such as for example a starter motor for an internal combustion engine.

Large internal combustion engines, such as marine engines and those used in heavy earth moving plant, require considerable energy to rotate their crankshafts during starting. Where other power is not available electric batteries are frequently used for this purpose but are liable to lose power for various reasons, e.g., if left unused for more than a short period of time. Furthermore the problem of starting becomes particularly acute in low-temperature conditions when the power of many electric batteries becomes very small.

SUMMARY OF THE INVENTION The present invention provides an apparatus which will function satisfactorily at relatively low temperatures, for example in freezing conditions and which will, at least in its preferred embodiments, retain almost indefinitely sufficient energy to start an internal combustion engine.

According to the present invention there is provided a hydraulic motor and actuating means therefor comprising means defining a first space capable of containing pressurised gas, means defining a second space capable of containing hydraulic liquid, wall means sealingly separating said first and second spaces, said wall means being constructed and arranged to permit changes in the volume of said first space, means for introducing pressurised hydraulic liquid in said second space so as to reduce the volume of said first space compressing the gas, said second space being connected to the hydraulic motor and valve means for controlling communication between said second space and the hydraulic motor.

In the use of such apparatus to actuate a hydraulic motor the said first space is filled with gas to a pressure less than, e.g., about 75 percent of, the operating pressure of the motor. Hydraulic liquid is then pumped into the second space to reduce the volume of the first space until the pressure in both spaces reaches the motor operating pressure, e.g., about 2,000 psi. Then, when the said valve means is actuated hydraulic liquid is driven towards the hydraulic motor as the first space expands towards its original volume.

Said wall means may be at least partly flexible and/or elastic. The said first and second spaces could be defined by separate chambers or housings. Preferably, however, the said spaces are both defined within a pressure vessel whose wall partly defines said second space.

The said wall means may be partly rigid; for example such means may comprise inner and outer rigid wall members connected by an annular flexible diaphragm, or a rigid wall member incorporating a flexible bellows. Preferably, however, the wall means is substantially wholly flexible and/or elastic. It may then comprise, for example, a flexible diaphragm dividing the said first and second spaces from one another. In a preferred embodiment, however, the said wall means is constituted by a flexible and elastic bag which defines said first space and is mounted in the aforementioned pressure vessel.

Preferably the said first and second spaces are. respectively capable of containing gas and hydraulic liquid at a pressure of at least 1,000 psi.

Preferably the said means for pressurising hydraulic liquid comprises a hand operable pump. Apparatus intended for use in starting an internal combustion engine preferably includes both such a hand pump and a pump adapted to be driven by the engine, such pumps preferably being connected in parallel. Particularly when an engine operated pump is provided, the apparatus preferably includes an off-loading valve arranged so that when said second space is fully charged hydraulic liquid from the said pressurising means is bypassed from the engine operated pump to the reservoir, so that the engine operated pump works under minimal load when the said second space is fully charged.

In apparatus intended for actuating a hydraulic starter motor the said valve means preferably comprises a control valve having a partly'open position for restricted flow of hydraulic liquid during initial actuation of a hydraulic motor and a fully open position for free flow. Then, in typical circumstances of use, as the control valve is opened the initial restricted flow of hydraulic liquid throws the starter pinion into engagement with the starter ring on the flywheel and thereafter the free flow of hydraulic liquid rotates the engine. This type of control valve also has the advantage that the engine can be rotated slowly if the control valve is set to its partly open position; this is useful when, for example, tappet clearances are'being adjusted or when diesel fuel systems are being bled.

Preferably nitrogen gas is used to pressurise the said first space so as to minimise risk of fire or explosion. Other gases which do not form explosive mixtures with hydraulic liquid could of course be used.

To retain the said second space in its charged condition for long periods of time a shut-off valve is preferably provided.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing shows, by way of example, one embodiment of apparatus in accordance with the present invention, for actuating a hydraulic starter motor for an internal combustion engine.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawing, the apparatus includes a pressure vessel 1 in which is mounted a flexible and elastic bag 2. The bag 2 defines a first space capable of containing gas under pressure and is made of reinforced rubber. The bag 2 is filled with nitrogen at a pressure of 1,500 psi through a check-valve 3 in a housing 4. The space 5 between the inside of pressure vessel 1 and the outside of bag 2 constitutes a second space capable of containing hydraulic liquid. Hydraulic liquid is stored in a reservoir 6 in which is mounted a pump 7 manually operable by a lever 8. The pump outlet is connected to pressure vessel 1 by a conduit 9 containing a check-valve 10. I

A gear pump 11 adapted to be driven by the engine to be started is connected in parallel with hand pump 7 and has a delivery line 12 connected to conduit 9 as shown. A check-valve 13 is disposed in conduit 12 for a purpose which is explained hereinafter.

An off-loading valve 14 operable by hydraulic pressure in pilot line 15 is connected to conduit 9 and is set to bypass hydraulic liquid from pumps 7 and 11 back to the reservoir when the pressure in pilot line 15 reaches 2,000 psi.

A spool valve 16 is situated between pressure vessel 1 and a hydraulic starter motor 17 having an operating pressure of 2,000 psi. The spool valve 16 is operated by a handle 18 which can be moved between positions 19, 20 and 21. The handle 18 is biased by a spring (not shown) into position 19 in which the spool valve is closed. As handle 18 is moved downwardly towards position 20 a passage for restricted flow of hydraulic liquid is progressively opened while as the handle 18 is moved between positions 20 and 21 a passage for free flow is opened. A return conduit 22 connects the low pressure side of hydraulic starter motor 17 to reservoir 6, which contains an oil strainer to prevent dirt from entering pumps 7 and 11.

Hydraulic starter motor 17 includes a bendix on which is mounted a starter pinion 23.

A hand wheel 24 operates a shut-off valve 25 situated in the base of pressure vessel 1.

For the purpose of describing the mode of operation of the apparatus shown in the drawing, it will be assumed that the above described apparatus is fitted to a marine engine and that pressure vessel 1 is not charged. Spool valve 16 is in its closed position and bag 2 is filled with nitrogen at 1,500 psi.

Shut-off valve 24 should first be opened. Upon reciprocating hand lever 8 hydraulic liquid 5 passes from reservoir 6 through conduit 9 into space 5 in pressure vessel 1. Since the hydraulic liquid is substantially incompressible the volume of bag 2 decreases, thereby increasing the pressure of the nitrogen in the bag 2. The pressures of nitrogen in the bag 2 and of hydraulic liquid in conduit 9 are substantially equal and as more hydraulic liquid is pumped into pressure vessel 1 the pressure in conduit 9 and pilot line 15 increases. Checkvalve 13 prevents hydraulic liquid returning to reservoir 6 via gear pump 1 1. When the pressure in pilot line 15 reaches 2,000 psi off-loading valve 14 operates to bypass hydraulic liquid directly to reservoir 6. When this occurs the force needed to opeate hand lever 8 drops considerably and signifies to the operator that the pressure vessel 1 is fully charged. Whereas the hydraulic pressure upstream of check-valve drops to a very low pressure, valve 10 ensures that the pressure in pilot line 15 remains at 2,000 psi until pressure vessel 1 is discharged.

When the hydraulic starter motor 17 is to be actuated the operator pushes handle 18 of spool-valve 16 downwardly towards position 20. This allows a restricted flow of hydraulic liquid to pass from pressure vessel 1 to hydraulic starter motor 17 and throws starter pinion 23 into engagement with the starter ring on the flywheel of the engine.

Further downwards movement of handle 18 rapidly increases the flow rate of hydraulic liquid through motor 17 and causes the crankshaft of the engine to rotate rapidly. The pressure vessel 1 is designed to hold sufficient hydraulic liquid to rotate the crankshaft about 9 revolutions. In the present case this takes about 1% seconds. Hydraulic liquid leaving the low pressure side of motor 17 returns to reservoir 6 through return conduit 22.

As pressure vessel 1 is discharged the pressure in pilot line 15 drops and off-loading valve 14 operates to close the bypass to reservoir 6.

When the engine fires, pinion 23 is thrown out ofengagement with the starter ring. Gear pump 11 rotates and delivers hydraulic liquid through delivery line 12 and conduit 9. Upon releasing handle 18 it returns under the influence of its return spring to position 19. The hydraulic liquid from gear pump 11 then enters pressure vessel 1 until the pressure in pilot line 15 again reaches 2,000 psi at which pressure off-loading valve 14 again operates to bypass hydraulic liquid to reservoir 6. When this occurs gear pump 11 still continues to circulate hydraulic liquid but is only very lightly loaded.

Because hydraulic liquid under high pressure tends over a long period of time to leak past spool valves, such as spool valve 16 described, shut-off valve 25 is provided which when closed will retain the pressure vessel 1 charged almost indefinitely. This ensures that even if an engine is not started for a long period there will be sufficient hydraulic liquid in the pressure vessel 2 to rotate the crankshaft several times.

Typically pressure vessel 2 has a capacity of l, 2 or 4 gallons for small marine engines. However, the ca-.

pacity of the vessel will vary according to the size of engine and the number of rotations it is desired to impart to the crankshaft thereof.

While a hydraulic starter motor having an operating pressure of 2,000 psi is described, other hydraulic motors having operation pressure, for example in the range l,0003,000 psi could also be used. It should be noted that the pressure of hydraulic fluid in the space 5 should not exceed the operating pressure of the motor for fear of damaging the motor.

Whereas the illustrated apparatus is particularly adapted to actuate a hydraulic starter motor, which is an example of a rotary hydraulic motor, it should be understood that apparatus according to the present invention could also be used to actuate a linear hydraulic motor, for example a hydraulic ram.

A specific application of the illustrated apparatus would be as a starter for a stand-by generator should the main electric power fail. In this case spoolvalve 16 is controlled by a solenoid which normally maintains handle 18 in position 19. Upon mains failure the solenoid ceases to hold handle 18 in position 19 and the handle 18 drops under its own weight through position 20 to position 21. This automatically starts the standbygenerator and provides a source of power.

Modifications of the above described embodiment are possible within the scope of the invention for example the pressure vessel containing the flexible bag may be replaced by means defining spaces for the pressurised gas and hydraulic fluid respectively and a cylinder connecting the spaces in which cylinder a piston is slidably mounted. Nitrogen is introduced into a space on one side of the piston and pressurized hydraulic liquid is then introduced into the space on the other side of the piston to compress the nitrogen.

1 claim:

1. A hydraulic starter system having a hydraulic starter motor with a starterv pinion and actuating means for the motor, the actuating means comprising:

a hydraulic accumulator having a first space capable of containing pressurized gas;

means defining a second space capable of containing hydraulic liquid, said second space being connected to the hydraulic motor;

wall means sealingly separating said first and second I spaces, said wall means being constructed and arranged to permit changes in volume of said first space; means for introducing pressurized hydraulic liquid into said second space so as to reduce the volume of said first space so as to compress the gas; and valve means for controlling communication between said second space and the hydraulic motor, said valve means having an inlet connected to said second space and an outlet connected to the hydraulic motor and said valve means including two discrete passages through which hydraulic liquid can flow from said second space to the hydraulic motor, one of said passages being adapted to permit a restricted flow of hydraulic liquid to cause a slow rotation of the hydraulic motor for causing the starter pinion to engage with a ring gear of an engine flywheel and the other of said passages being adapted to permit an increased flow of hydraulic liquid to the hydraulic motor to cause rapid rotation of the motor, and means for bringing the passages sequentially into communication between said inlet and outlet of said valve means. 2. The combination as claimed in claim 1, wherein said wall means is at least partly flexible and/or elastic. 3. The combination as claimed in claim 1, wherein said first and second spaces are both defined within a pressure vessel whose wall partly defines said second space. A

4. The combination as claimed in claim 3, wherein said first space is defined by a flexible and elastic bag mounted in said pressure vessel and constituting said wall means.

5. The combination as claimed in claim 4, wherein said bag is made of reinforced rubber.

6. The combination as claimed in claim 1, wherein said first and second spaces are respectively capable of containing gas and hydraulic liquid at a pressure of at least 1,000 psi.

7. The combination as claimed in claim 1, wherein said means for introducing pressurized hydraulic liquid into said second space comprises a hand operable pump.

8. The combination as claimed in claim 7, wherein said means for introducing pressurized hydraulic liquid into said second space further comprising a pump adapted to be driven by an internal combustion engine.

9. The combination as, claimed in claim 8, wherein said pumps are connected in parallel.

10. The combination as claimed in claim 1 further including an off-loading valve for automatically bypassing hydraulic liquid from said liquid pressurizing means back to a reservoir when the pressure of hydraulic liquid in said second space reaches a predetermined value.

11. The combination as claimed in claim 1, wherein said valve means further comprises a shut-off valve for retaining pressurized hydraulic liquid in said second space over prolonged periods.

12. An internal combustion engine having the combination of a hydraulic starter system as claimed in claim 1. 

1. A hydraulic starter system having a hydraulic starter motor with a starter pinion and actuating means for the motor, the actuating means comprising: a hydraulic accumulator having a first space capable of containing pressurized gas; means defining a second space capable of containing hydraulic liquid, said second space being connected to the hydraulic motor; wall means sealingly separating said first and second spaces, said wall means being constructed and arranged to permit changes in volume of said first space; means for introducing pressurized hydraulic liquid into said second space so as to reduce the volume of said first space so as to compress the gas; and valve means for controlling communication between said second space and the hydraulic motor, said valve means having an inlet connected to said second space and an outlet connected to the hydraulic motor and said valve means including two discrete passages through which hydraulic liquid can flow from said second space to the hydraulic motor, one of said passages being adapted to permit a restricted flow of hydraulic liquid to cause a slow rotation of the hydraulic motor for causing the starter pinion to engage with a ring gear of an engine flywheel and the other of said passages being adapted to permit an increased flow of hydraulic liquid to the hydraulic motor to cause rapid rotation of the motor, and means for bringing the passages sequentially into communication between said inlet and outlet of said valve means.
 2. The combination as claimed in claim 1, wherein said wall means is at least partly flexible and/or elastic.
 3. The combination as claimed in claim 1, wherein said first and second spaces are both defined within a pressure vessel whose wall partly defines said second space.
 4. The combination as claimed in claim 3, wherein said first space is defined by a flexible and elastic bag mounted in said pressure vessel and constituting said wall means.
 5. The combination as claimed in claim 4, wherein said bag is made of reinforced rubber.
 6. The combination as claimed in claim 1, wherein said first and second spaces are respectively capable of containing gas and hydraulic liquid at a pressure of at least 1,000 psi.
 7. The combination as claimed in claim 1, wherein said means for introducing pressurized hydraulic liquid into said second space comprises a hand operable pump.
 8. The combination as claimed in claim 7, wherein said means for introducing pressurized hydraulic liquid into said second space further comprising a pump adapted to be driven by an internal combustion engine.
 9. The combination as claimed in claim 8, wherein said pumps are connected in parallel.
 10. The combination as claimed in claim 1 further including an off-loading valve for automatically bypassing hydraulic liquid from said liquid pressurizing means back to a reservoir when the pressure of hydraulic liquid in said second space reaches a predetermined value.
 11. The combination as claimed in claim 1, wherein said valve means further comprises a shut-off valve for retaining pressurized hydraulic liquid in said second space over prolonged periods.
 12. An internal combustion engine having the combination of a hydraulic starter system as claimed in claim
 1. 